Gas absorbents have been used in various fields, for example, for preservation of vacuum, removal of a trace amount of gas in rare gas, and removal of gas in fluorescent lamp.
As for rare gases used in semiconductor production industry, there is a demand for purification of the rare gases by removal of nitrogen, hydrocarbon, carbon monoxide, carbon dioxide, oxygen, hydrogen, steam and the like contained in the rare gases. In particular, it is quite difficult to remove nitrogen, the most stable molecule among them, at around room temperature.
An example of the material for removal of nitrogen or hydrocarbons contained in rare gas is a getter material of a ternary alloy of zirconium, vanadium and tungsten (see, for example, Patent Document 1).
The ternary alloy removes a trace amount of impurities such as nitrogen contained in rare gas at a temperature of 100 to 600° C., when brought into contact with the rare gas.
Non-vaporizing getter alloys having a high gas absorption capacity to nitrogen include alloys containing zirconium, iron, manganese, yttrium or lanthanum, and a rare earth element (see, for example, Patent Document 2).
The non-vaporizing getter alloy having a high gas absorption capacity to nitrogen becomes active at room temperature to gases such as hydrogen, hydrocarbon and nitrogen etc., when activated at a temperature of 300 to 500° C. for 10 to 20 minutes.
Alternatively, alloys used for removal of nitrogen at low temperature include Ba—Li alloys (see, for example, Patent Document 3).
The Ba—Li alloy is used as a device for preserving vacuum together with a drying agent in an insulated jacket and shows reactivity to gases such as nitrogen at room temperature.
Alternatively, an absorbent of copper ion-exchanged ZMS-5 zeolite is known as a material for removal of impurities such as nitrogen contained in a gas to be purified (see, for example, Patent Document 4).
It is produced by introducing copper ion into a ZMS-5 zeolite and heat-treating the zeolite by a conventional ion exchange method for nitrogen absorption activity, and the maximum nitrogen absorption capacity at an equilibrium pressure of 10 Pa is reported to be 0.238 mol/kg (5.33 cc/g).    Patent Document 1: Japanese Unexamined Patent Publication No. 6-135707    Patent Document 2: Japanese Unexamined Patent Publication No. 2003-535218    Patent Document 3: Japanese Unexamined Patent Publication No. 9-512088    Patent Document 4: Japanese Unexamined Patent Publication No. 2003-311148